EPR STUDY OF PHOSPHAFULVENE RADICAL-ANIONS

Cyclic voltammetry of phosphafulvene and dibenzophosphafulvene shows t hat in DMF these compounds are reduced at -1.200 and -1.349 V, respect ively. The EPR spectra of the corresponding radical anions, formed by electrochemical reduction or by reaction on a potassium mirror, are re corded between 110 K and room temperature. The g and P-31 hyperfine te nsors are measured and compared to those previously obtained for a pho sphaalkene radical anion. Ab initio investigations on model phosphaalk ene and phosphafulvene radical anions show that, in accord with the ex perimental results, the electronic structure of these two species are quite different: whereas the unpaired electron is delocalized on the w hole P=C(H)R moiety in the phosphaalkenic anion, it is markedly locali zed on the phosphorus atom in the phosphafulvene anion. Calculated spi n densities and charge distributions for phosphafulvene and azafulvene anions are compared.